Somebody in a garage today is working on a business that will be worth billions within 5 years, and we'll all kick ourselves with "why didn't we think of that!"

Right, but for everyone of those people, there are 1,000 other people just as smart also working on good ideas that are going nowhere fast.

I'm not sure if you're agreeing or disagreeing or neither.

But I think the "why didn't I think of that guy" is mostly luck.

Lots of people are smart and work hard and don't really get anywhere.

Smart and Work Hard are only two of the 5+ components needed for success, of which Luck, Opportunity and Timing also belong. I'm sure there's more.

What is timing beside luck?

The founders had a good bit of luck, but then hired a lot of super smart people fresh out of college.